Hi Father. I'm sorry you're in this place and sorry for what your son has put you through. I've been through all of this, different substances, but basically the same. First off, get yourself to a NarAnon or AlAnon meeting and don't quit till you find a group that you can relate to.
I GPS'ed my kid for years. We prevented a lot of drunk driving. We also spent countless hours filled with anxiety trailing him, trapping him, pulling him out of the car. Ironically, he switched cars and before we could hardwire the GPS back in, he got a DUI. It didn't cure him from drinking but it was a HUGE wake up call. He needed to feel the consequences himself. He couldn't drive for 6 months and had to pay everything related to it himself, retain the lawyer and go to court by himself.
He us currently on Antabuse which helps tremendously. I would recommend Vivitrol but it is ridiculously expensive if your insurance doesn't pay for it,
Yes, there are probably tons of underlying conditions but ultimately all of it has to be your sons willingness to get better. Even after all we've been through I know my son wants to be like all the other young adults he sees who drink, but don't seem to get in any trouble, or who know when to stop. (My son is a binger).
We too have gone the route of gradual independence. My son moved an hour away to go to grad school. The rules are simple. Drinking and driving = car will be sold. Arrest = no contact. We had to draw the line.
I've also had to give up my surveillance. It may cost me in the long run but with AlAnon I've been able to find a measure of peace. Like your son, my son does very well in school. . I do not know what the future holds but I can't change it. He knows we love him and have his best interests at heart, but he is an adult and chooses his path. One day I think he'll make it, the next I don't. But I have lost myself so much over the past 5 years that I and everyone around me suffers.
Please keep in touch on SR. This place has been invaluable to me. No one on here can fix the problem but we can help save your sanity.